A light-emitting diode (LED) is an energy efficient solid state light (SSL) source, which is currently used in a wide variety of lighting applications. A feature in common for all these applications is that the LEDs involved need to be driven by an electrical power supply in order to have the LEDs emit light. According to a widely known technique wired LEDs (i.e. LEDs being provided with ‘galvanic’ conducting leads) may be powered by a direct current (DC). This technique requires the use of thin metal wires, which are soldered or glued to one or both of the electrical terminals of the LEDs. The LEDs may also be soldered directly (wireless) on a printed circuit board (PCB).
A more recent technique for powering LEDs is based on so-called ‘capacitive driving’ in which an alternating current (AC) is applied. In this technique pairs of so-called anti-parallel oriented LEDs are used. In such a LED pair, the cathode of one of the LEDs is electrically connected to the anode of the other LED, whereas the anode of the one LED is electrically connected to the cathode of the other LED. In this respect, it should be realized that LEDs are electrical components or diodes having a polarity, meaning that a relevant electrical current can flow through a LED only in one direction, the opposite direction being blocked.
LED packages suitable for capacitive driving are known as such, for example from the patent application published as US2008/0218095A1. More particularly FIG. 2B in this document shows a cross-section of such a package, which essentially comprises a capacitor composed of a dielectric substrate sandwiched between two conductive plates. An anti-parallel oriented LED structure is electrically connected to one of these plates and thermally coupled to the substrate. Various connector wires are present for capacitive driving of the described LED package.
Although the known LED package has proved to function satisfactorally, its design requires a relatively bulky structure. This causes that miniaturization of the known LED package is a difficult task. Moreover, the presence of conducting wires in the known package usually requires soldering techniques. However, in such structures solder connections are apt to degrade over time due to the relatively high temperatures produced by LEDs when they are powered to emit light.